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I have one, it helps keep nuissance algaes down if set up right(very low flow)
Some say it helped rid or keep away ich, possibly helps.
Some will say it can kill pods, maybe, but my setup is before fuge, pods enter display a plenty.

If you want a Fish Only With Live Rock and Coral (FOWLRC) it may be fine. If you want a reef, you want diversity, and it will absolutely reduce the diversity of microorganisms in your tank, such as pelagic bacteria. Seeing that bacterioplankton is a primary source of food for corals, and corals are literally walls of mouths, suggesting they do indeed like to capture this floating food, I'm not sure why you would want to kill it off. Your corals may be ok, you can throw more light at them and they can get more nutrients from their symbiotic algae. You probably won't see mortality as a result, but that does not mean it is not negatively effecting them. It will cut into the food web.

The only benefit show is that it may reduce floating algae, spores etc... It is not show to reduce any disease in a closed system. It will require energy and light bulbs every 6 months or so.

If you are happy with a FOWLRC and don't mind the extra maintenance, it may be worth it. For many people a FOWLRC is probably all they really want. It has no place in a diverse reef though. I dose carbon and silicates. these reduce nutrients by adding to the food web and as a result I maybe clean my glass with a magnet once every two weeks. Don't need UV to accomplish that.

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Our imagination is stretched to the utmost, not, as in fiction, to imagine things which are not really there, but just to comprehend those things which are there. ~Richard Feynman

I completely disagree w/ m2434's comment, I've seen many nice reefs w/ a UV, but expect this topic to be debated, as always...
I run a Current gamma 15w
I've had many mixed reefs w/ them, nems, sps, never had an issue keeping either.

I completely disagree w/ m2434's comment, I've seen many nice reefs w/ a UV, but expect this topic to be debated, as always...
I run a Current gamma 15w
I've had many mixed reefs w/ them, nems, sps, never had an issue keeping either.

What comments do you completely disagree with? I never said you can't have nems, sps, etc... I said 4 things.

Said another way, these 4 things are as follows.

1) Your diversity of plagic bacteria, which are a key component of a natural reef, will be limited. However, I said you should be able to compensate with extra light. BTW, this is common in the hobby as plagic bacteria is already fairly limited, but why limit it it more?

2) A uv has only been shown to limit floating microorganisms, and has not been shown to reduce disease in our types of systems.

3) It requires extra maintenance.

4) you can accomplish the same results with other methods, which IMO have more benefits.

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Our imagination is stretched to the utmost, not, as in fiction, to imagine things which are not really there, but just to comprehend those things which are there. ~Richard Feynman

You can use a UV 2 ways.. Water polishing and sterilization. Sterilization occurs at lower flow rates where polishing will also occur. Polishing without sterilization can occur at higher flow rates.

Most decent UV units have flow charts that will tell you what various flow rates through their unit will acomplish. Personally, if you have fish in your system, I think UV is very benificial. I can tell you from experience that they do make an immediate difference in water clarity even at higher flow rates that are less harmful to free floating organisms.

That said, I run one on my reef tank and am very happy with the results. If I didnt have fish, I might not use one but I dont know too many reeftanks that dont have fish in them.

ive never ran a uv on any of my saltwater tanks. Mostly because when I started everyone always says it kills beneficial bacteria..So I've never felt one necessary and everytime I picked one up in any kind of tank deal I just sold it for a nice profit=). I keep my parameters in check and I never have any nuissance(sp) algae. Occasionally from time to time my Kole tang get ich I feed heavy and soak the food with garlic and its gone (well not showing signs)in a few days.. would a UV stop the ich..I dunno maybe but I still dont feel one necessary.. Just seems like extra money I don't need to spend on my tank.. I do however run a big 5ft tall UV on my 10,000gallon koi pond and that is why my pond even being how huge it is NEVER ever gets any nasty algae the water is always crystal clear and you can see to airdiffuser on my 4" drain... I had a new bulb go bad on it this past summer went bad after 60 days of course the warranty was only 30days.. and the pond turned into a nasty mess I couldn't even see the fish.. took a week to figure out it actually was the UV since I had just replaced it.. replaced it again after about a week and a half the pond is perfect again..

I think you misread my comment, I said Fish Only With Live Rock and Coral (FOWLRC). My point on that was a reef is a diverse ecosystem. The less of an ecosystem it is, the tougher it is to justify calling it a reef. It may be a diverse aquarium, with fish, corals, and benthic organisms, however, the pelagic organisms that complete the reef will are going to be significantly thinned out by the UV, if not eliminated. So, it is not going to have all of the components of a complete reef.

I'm sure many people don't care about this though and in practice it probably does make little to no noticeable difference. However, it should be pointed out, as there is as much, or more evidence to show this would be detrimental, as there is evidence to show any of the possible effects of UV are beneficial.

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Our imagination is stretched to the utmost, not, as in fiction, to imagine things which are not really there, but just to comprehend those things which are there. ~Richard Feynman

BTW, beautiful tanks guys. I know people have strong opinions on this. I certainly do and believe it is unnecessary at best and possibly detrimental to some extent at worst. I know others disagree and I do respect that. I think if you are aware of the possible benefits and consequences then your decision is a fine one. So, I'm just trying to provide a different view, you don't have to agree

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Our imagination is stretched to the utmost, not, as in fiction, to imagine things which are not really there, but just to comprehend those things which are there. ~Richard Feynman

Several years ago I added a UV system to my reef. I added a large volume system Dual 54w 30" Tubes plumbed for 2".

I got it as an insurance policy, at the time the system was doing really well. I can't say that I noticed any differences. There was definitely no negative changes in the system. However, please be aware that in a healthy properly balanced reef, the efficiency of the UV is constantly decreasing because the UV tubes are constantly getting calcified.

So if you are considering this, make sure you find a unit that is easy to dissassemble and you plumb it so you have lots of easy access to dissassemble and clean the unit. Also the parts of a UV system are fragile (glass tubes). Shop for a UV unit where the parts are very available, and even include in your purchase a spare tube, bulb and gasket collection.

To throw another wrench into the discussion, depending on what you are trying to accomplish with the UV, see if ozone is a better option. I am a huge believer in the use of ozone, and it is alot less maintenance.

I run UV on both my Reef Systems and the water is clearer and it helps nuke ick when in the free floating stage. I think Emperor Aquatics has the best literature that explains how to set a system to clarify, or kill pathogens. I still have pods and most of the benificial bacteria live within the Rock and Substrate. I feel most people who see no benifit use a undersized unit with the wrong amount of flow. I run the UV filter on a closed loop and my refugium overflows into my main display so pods seem to be prolific. In my opinion when sized properly a UV filter is very benificial to a closed system.

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Scott Steinberger
SCMAS/SCRK/MASNA member
There is more than One Way to skin a Reef!

It's all good, there are alot of ways/methods and some have different terminolgy/definitions/symantics.(sp?)
I try to keep an open mind, but yeah, most of us are pretty passionate about our hobby and our ways to achieve long term success.
It's all learning through discussion and sharing experiences, and those will vary.

Thank you guys for a lot of info and great debate.I was thinking of mostly using UV to polish water in my tank and also have few small spots of cyano,I have read that UV helps with it.I have no problem with algae or any disease .I also use biopellets so I assume that there always be new source of bacteria for my corals to feed on.